<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>颜色显示切换</title>
    <style>
        #box {
            width: 200px;
            height: 200px;
            background-color: skyblue;
        }
    </style>
</head>

<body>
    <div id="box"></div>
    <button id="btn">显示/隐藏</button>
    <script>
        let isShow = true; // 记录盒子是否显示，默认true代表显示
        // 1. 找到id=btn的元素
        let btnEle = document.getElementById("btn");
        let boxEle = document.getElementById("box");
        // 2. 给其绑定单击事件
        btnEle.addEventListener("click", function () {
            if (isShow) {
                boxEle.style.display = "none"; // 隐藏
                //   isShow = false;
            } else {
                boxEle.style.display = ""; // 显示
                //   isShow = true;
            }

            isShow = !isShow; // 取反操作
        });
    </script>
</body>

</html>